One in 10 patients are now waiting for over four hours in A&E during June, July and August in English hospitals.
Government figures reveal that A&E waiting times this summer have been worse than every winter for the past 12 years bar one.
Only last winter saw a worse performance since the target started in 2004.
During the summer months 90.6% of patients were seen in four hours, figures from NHS England show, as compared with the target of 95% in four hours.
The data also showed hospitals are missing a number of other key targets for cancer, routine operations and ambulance response times.
Dr Mark Holland, president of the Society for Acute Medicine, said: “The NHS is on its knees and, this winter, areas will implode around the country. There is no reserve left.
“Over the coming weeks and months, if we see a major increase in admissions due to flu or bed closures due to norovirus, we will collapse.”
Delayed discharges have also hit a high. There were over 188,000 days of delays in August – a 30% rise on the same month the year before.
The figures follow the CQC’s annual report which revealed that safety concerns have been raised about two-thirds of A&E units in England, with inspectors blaming underfunding of council care services for causing overcrowding in hospitals.
Dr Anthea Mowat, BMA representative body chair, said: “We can only address the problem by looking at the health and social care system as a whole. We can only get to grips with pressure on A&Es if every part of the system – from our GP surgeries, to hospitals, to community care – is fully supported and working well, which includes urgently addressing the workforce crisis facing our health service.
“To protect the future of the NHS, the government must produce a long term strategy that addresses the fundamental workload, staffing and funding challenges that are currently overwhelming services.”
The CQC said emergency care was one of the poorest-performing parts of the system.
Dr Taj Hassan, President of the Royal College of Emergency Medicine, said: “This timely report is welcome as it describes that we have seemingly reached a tipping point in how adult social care is financed and delivered.
“The provision of social care has a huge impact on the performance of Emergency Departments. Figures published today bear this out. August saw a record number of delayed days and a third of this is attributable to a lack of social care.
“The report shows how failed systems are having a dramatic impact on secondary care. These failures in the community are showing that this results in Emergency Departments becoming overcrowded due to exit block from lack of access to hospital beds and then patients being delayed from getting back into the community. Exit block overcrowding causes delays to essential treatment in the ED and significantly raises the risk of death.
“We urge Government for the need for wider investment both in emergency care as well as social care.”